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Abstract
A mobile profiling system has been developed that is capable of probing the atmosphere from the surface to over 30 km. The Mobile Profiling System (MPS) combines ground-based instruments, including a five-beam 924-MHz radar wind profiler, a radio acoustic sounding system, and two passive microwave sounders, with a receiver and processor for meteorological satellite data. Software in the MPS produces profiles from the surface to the highest satellite sounding level by combining surface data and profiles generated from the suite of ground-based sensors with those from a meteorological satellite. The algorithms generate soundings of temperature, humidity, wind velocity, and other meteorological variables. The method for combining data from the separate sources is not site specific and requires no a priori information. The MPS has the potential for a variety of applications, including detailed analysis of meteorological variables for research and operations over mesoscale areas, such as regional pollution studies and severe storm forecasting. This paper describes the method for merging data from satellite and ground-based remote sensing systems, and presents results from a series of field tests of both individual sensors and combined soundings. Accuracy of the combined soundings appears comparable to that from rawinsonde with the exception of wind velocity at satellite sounding altitudes. The MPS has operated successfully in several different climates: in the Los Angeles Free Radical Experiment at Claremont, California, and in tests at White Sands Missile Range, New Mexico; Erie, Colorado; Ft. Sill, Oklahoma; and Wallops Island, Virginia.
Abstract
A mobile profiling system has been developed that is capable of probing the atmosphere from the surface to over 30 km. The Mobile Profiling System (MPS) combines ground-based instruments, including a five-beam 924-MHz radar wind profiler, a radio acoustic sounding system, and two passive microwave sounders, with a receiver and processor for meteorological satellite data. Software in the MPS produces profiles from the surface to the highest satellite sounding level by combining surface data and profiles generated from the suite of ground-based sensors with those from a meteorological satellite. The algorithms generate soundings of temperature, humidity, wind velocity, and other meteorological variables. The method for combining data from the separate sources is not site specific and requires no a priori information. The MPS has the potential for a variety of applications, including detailed analysis of meteorological variables for research and operations over mesoscale areas, such as regional pollution studies and severe storm forecasting. This paper describes the method for merging data from satellite and ground-based remote sensing systems, and presents results from a series of field tests of both individual sensors and combined soundings. Accuracy of the combined soundings appears comparable to that from rawinsonde with the exception of wind velocity at satellite sounding altitudes. The MPS has operated successfully in several different climates: in the Los Angeles Free Radical Experiment at Claremont, California, and in tests at White Sands Missile Range, New Mexico; Erie, Colorado; Ft. Sill, Oklahoma; and Wallops Island, Virginia.
Abstract
Denver's Continuous Air Monitoring Program (CAMP) site, typically recording the highest carbon monoxide levels in the metropolitan area; lies within a large region of downtown Denver shadowed by tall buildings. Two studies conducted during the winters of 1987/88 and 1988/89 indicated several possible scenarios leading to the high-pollution episodes often reported at CAMP. Sodar records and stability calculations at CAMP indicate that building shadows may be a contributing factor. The building shadowing was simulated by a computer model and its effects were examined from 2 days of detailed vertical temperature profiles taken in the vicinity of CAMP. The vertical temperature structure was mapped both spatially and temporally as it pertains to the shadowed and unshadowed regions. Results show that shadowing at CAMP is quickly followed by the formation of a shadow surface-based inversion and a local rise in carbon monoxide concentrations. Strength of the inversion depends on the meteorology and surface albedo and relates to a difference in solar radiation intensity of >100 W m−2 between shadowed and unshadowed regions.
Abstract
Denver's Continuous Air Monitoring Program (CAMP) site, typically recording the highest carbon monoxide levels in the metropolitan area; lies within a large region of downtown Denver shadowed by tall buildings. Two studies conducted during the winters of 1987/88 and 1988/89 indicated several possible scenarios leading to the high-pollution episodes often reported at CAMP. Sodar records and stability calculations at CAMP indicate that building shadows may be a contributing factor. The building shadowing was simulated by a computer model and its effects were examined from 2 days of detailed vertical temperature profiles taken in the vicinity of CAMP. The vertical temperature structure was mapped both spatially and temporally as it pertains to the shadowed and unshadowed regions. Results show that shadowing at CAMP is quickly followed by the formation of a shadow surface-based inversion and a local rise in carbon monoxide concentrations. Strength of the inversion depends on the meteorology and surface albedo and relates to a difference in solar radiation intensity of >100 W m−2 between shadowed and unshadowed regions.
Abstract
The need for a reliable, low-cost observing system to measure water vapor in the atmosphere is incontrovertible. Experiments have shown the potential for using Global Positioning System (GPS) receivers to measure total precipitable water vapor accurately at different locations and times of year and under all weather conditions. The National Oceanic and Atmospheric Administrations’s (NOAA) Forecast Systems Laboratory (FSL) and Environmental Technology Laboratory (ETL), in collaboration with the University NAVSTAR Consortium, University of Hawaii, Scripps Institution of Oceanography, and NOAA’s National Geodetic Survey (NGS) Laboratory, are addressing this need by developing a ground-based water vapor observing system based on the measurement of GPS signal delays caused by water vapor in the atmosphere. The NOAA GPS Integrated Precipitable Water Vapor (NOAA GPS–IPW) network currently has 35 continuously operating stations and is expected to expand into a 200-station demonstration network by 2004. This paper describes the major accomplishments of the project since its inception in 1994. Results from the analysis of the effect of satellite orbit accuracies on IPW accuracy are discussed. Several comparisons with collocated remote and in situ measurements, including radiosondes and ground- and space-based radiometers are shown. Results from preliminary model runs using the FSL Forecast Research Division’s Mesoscale Analysis and Prediction System (MAPS) model are presented. This work shows the feasibility of an operational system using GPS to continuously monitor atmospheric water vapor in near–real time with accuracies (<1.5 cm) comparable to radiosondes and water vapor radiometers.
Abstract
The need for a reliable, low-cost observing system to measure water vapor in the atmosphere is incontrovertible. Experiments have shown the potential for using Global Positioning System (GPS) receivers to measure total precipitable water vapor accurately at different locations and times of year and under all weather conditions. The National Oceanic and Atmospheric Administrations’s (NOAA) Forecast Systems Laboratory (FSL) and Environmental Technology Laboratory (ETL), in collaboration with the University NAVSTAR Consortium, University of Hawaii, Scripps Institution of Oceanography, and NOAA’s National Geodetic Survey (NGS) Laboratory, are addressing this need by developing a ground-based water vapor observing system based on the measurement of GPS signal delays caused by water vapor in the atmosphere. The NOAA GPS Integrated Precipitable Water Vapor (NOAA GPS–IPW) network currently has 35 continuously operating stations and is expected to expand into a 200-station demonstration network by 2004. This paper describes the major accomplishments of the project since its inception in 1994. Results from the analysis of the effect of satellite orbit accuracies on IPW accuracy are discussed. Several comparisons with collocated remote and in situ measurements, including radiosondes and ground- and space-based radiometers are shown. Results from preliminary model runs using the FSL Forecast Research Division’s Mesoscale Analysis and Prediction System (MAPS) model are presented. This work shows the feasibility of an operational system using GPS to continuously monitor atmospheric water vapor in near–real time with accuracies (<1.5 cm) comparable to radiosondes and water vapor radiometers.
Abstract
Bragg backscatter of radar waves from elevated turbulent layers is very highly correlated with the height profile of the gradient of radio refractive index through elevated turbulent layers, as has often been documented in past research. However, many users need profiles of radio refractive index or the associated humidity rather than profiles of their gradients. Simple integration of the gradients is usually not feasible because clutter and various noise sources often severely contaminate the lower-range gates. The authors show that if the total integrated humidity is independently available [for example, from the Global Positioning System (GPS)] and if the surface value of humidity is known, the profiles of humidity are retrievable with good accuracy. This method is demonstrated with data collected in Southern California, where 7 h of 449-MHz data were recorded along with GPS data. Three radiosonde balloons were launched during that period, and the profiles of humidity from the two sources are compared. Simulations are used to assess errors that result from factors such as lack of the sign of the humidity gradients. In conclusion, a humidity profile found by statistical retrieval is compared with one found by the technique proposed in this paper.
Abstract
Bragg backscatter of radar waves from elevated turbulent layers is very highly correlated with the height profile of the gradient of radio refractive index through elevated turbulent layers, as has often been documented in past research. However, many users need profiles of radio refractive index or the associated humidity rather than profiles of their gradients. Simple integration of the gradients is usually not feasible because clutter and various noise sources often severely contaminate the lower-range gates. The authors show that if the total integrated humidity is independently available [for example, from the Global Positioning System (GPS)] and if the surface value of humidity is known, the profiles of humidity are retrievable with good accuracy. This method is demonstrated with data collected in Southern California, where 7 h of 449-MHz data were recorded along with GPS data. Three radiosonde balloons were launched during that period, and the profiles of humidity from the two sources are compared. Simulations are used to assess errors that result from factors such as lack of the sign of the humidity gradients. In conclusion, a humidity profile found by statistical retrieval is compared with one found by the technique proposed in this paper.
Abstract
A new dataset synthesizes in situ and remote sensing observations from research ships deployed to the southeastern tropical Pacific stratocumulus region for 7 years in boreal fall. Surface meteorology, turbulent and radiative fluxes, aerosols, cloud properties, and rawinsonde profiles were measured on nine ship transects along 20°S from 75° to 85°W. Fluxes at the ocean surface are essential to the equilibrium SST. Solar radiation is the only warming net heat flux, with 180–200 W m−2 in boreal fall. The strongest cooling is evaporation (60–100 W m−2), followed by net thermal infrared radiation (30 W m−2) and sensible heat flux (<10 W m−2). The 70 W m−2 imbalance of heating at the surface reflects the seasonal SST tendency and some 30 W m−2 cooling that is mostly due to ocean transport.
Coupled models simulate significant SST errors in the eastern tropical Pacific Ocean. Three different observation-based gridded ocean surface flux products agree with ship and buoy observations, while fluxes simulated by 15 Coupled Model Intercomparison Project phase 3 [CMIP3; used for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report] general circulation models have relatively large errors. This suggests the gridded observation-based flux datasets are sufficiently accurate for verifying coupled models. Longwave cooling and solar warming are correlated among model simulations, consistent with cloud radiative forcing and low cloud amount differences. In those simulations with excessive solar heating, elevated SST also results in larger evaporation and longwave cooling to compensate for the solar excess. Excessive turbulent heat fluxes (10–90 W m−2 cooling, mostly evaporation) are the largest errors in simulations once the compensation between solar and longwave radiation is taken into account. In addition to excessive solar warming and evaporation, models simulate too little oceanic residual cooling in the southeastern tropical Pacific Ocean.
Abstract
A new dataset synthesizes in situ and remote sensing observations from research ships deployed to the southeastern tropical Pacific stratocumulus region for 7 years in boreal fall. Surface meteorology, turbulent and radiative fluxes, aerosols, cloud properties, and rawinsonde profiles were measured on nine ship transects along 20°S from 75° to 85°W. Fluxes at the ocean surface are essential to the equilibrium SST. Solar radiation is the only warming net heat flux, with 180–200 W m−2 in boreal fall. The strongest cooling is evaporation (60–100 W m−2), followed by net thermal infrared radiation (30 W m−2) and sensible heat flux (<10 W m−2). The 70 W m−2 imbalance of heating at the surface reflects the seasonal SST tendency and some 30 W m−2 cooling that is mostly due to ocean transport.
Coupled models simulate significant SST errors in the eastern tropical Pacific Ocean. Three different observation-based gridded ocean surface flux products agree with ship and buoy observations, while fluxes simulated by 15 Coupled Model Intercomparison Project phase 3 [CMIP3; used for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report] general circulation models have relatively large errors. This suggests the gridded observation-based flux datasets are sufficiently accurate for verifying coupled models. Longwave cooling and solar warming are correlated among model simulations, consistent with cloud radiative forcing and low cloud amount differences. In those simulations with excessive solar heating, elevated SST also results in larger evaporation and longwave cooling to compensate for the solar excess. Excessive turbulent heat fluxes (10–90 W m−2 cooling, mostly evaporation) are the largest errors in simulations once the compensation between solar and longwave radiation is taken into account. In addition to excessive solar warming and evaporation, models simulate too little oceanic residual cooling in the southeastern tropical Pacific Ocean.
Abstract
Surface flux, wind profiler, oceanic temperature and salinity, and atmospheric moisture, cloud, and wind observations gathered from the R/V Altair during the North American Monsoon Experiment (NAME) are presented. The vessel was positioned at the mouth of the Gulf of California halfway between La Paz and Mazatlan (∼23.5°N, 108°W), from 7 July to 11 August 2004, with a break from 22 to 27 July. Experiment-mean findings include a net heat input from the atmosphere into the ocean of 70 W m−2. The dominant cooling was an experiment-mean latent heat flux of 108 W m−2, equivalent to an evaporation rate of 0.16 mm h−1. Total accumulated rainfall amounted to 42 mm. The oceanic mixed layer had a depth of approximately 20 m and both warmed and freshened during the experiment, despite a dominance of evaporation over local precipitation. The mean atmospheric boundary layer depth was approximately 410 m, deepening with time from an initial value of 350 m. The mean near-surface relative humidity was 66%, increasing to 73% at the top of the boundary layer. The rawinsondes documented an additional moist layer between 2- and 3-km altitude associated with a land–sea breeze, and a broad moist layer at 5–6 km associated with land-based convective outflow. The observational period included a strong gulf surge around 13 July associated with the onset of the summer monsoon in southern Arizona. During this surge, mean 1000–700-hPa winds reached 12 m s−1, net surface fluxes approached zero, and the atmosphere moistened significantly but little rainfall occurred. The experiment-mean wind diurnal cycle was dominated by mainland Mexico and consisted of a near-surface westerly sea breeze along with two easterly return flows, one at 2–3 km and another at 5–6 km. Each of these altitudes experienced nighttime cloudiness. The corresponding modulation of the radiative cloud forcing diurnal cycle provided a slight positive feedback upon the sea surface temperature. Two findings were notable. One was an advective warming of over 1°C in the oceanic mixed layer temperature associated with the 13 July surge. The second was the high nighttime cloud cover fraction at 5–6 km, dissipating during the day. These clouds appeared to be thin, stratiform, slightly supercooled liquid-phase clouds. The preference for the liquid phase increases the likelihood that the clouds can be advected farther from their source and thereby contribute to a higher-altitude horizontal moisture flux into the United States.
Abstract
Surface flux, wind profiler, oceanic temperature and salinity, and atmospheric moisture, cloud, and wind observations gathered from the R/V Altair during the North American Monsoon Experiment (NAME) are presented. The vessel was positioned at the mouth of the Gulf of California halfway between La Paz and Mazatlan (∼23.5°N, 108°W), from 7 July to 11 August 2004, with a break from 22 to 27 July. Experiment-mean findings include a net heat input from the atmosphere into the ocean of 70 W m−2. The dominant cooling was an experiment-mean latent heat flux of 108 W m−2, equivalent to an evaporation rate of 0.16 mm h−1. Total accumulated rainfall amounted to 42 mm. The oceanic mixed layer had a depth of approximately 20 m and both warmed and freshened during the experiment, despite a dominance of evaporation over local precipitation. The mean atmospheric boundary layer depth was approximately 410 m, deepening with time from an initial value of 350 m. The mean near-surface relative humidity was 66%, increasing to 73% at the top of the boundary layer. The rawinsondes documented an additional moist layer between 2- and 3-km altitude associated with a land–sea breeze, and a broad moist layer at 5–6 km associated with land-based convective outflow. The observational period included a strong gulf surge around 13 July associated with the onset of the summer monsoon in southern Arizona. During this surge, mean 1000–700-hPa winds reached 12 m s−1, net surface fluxes approached zero, and the atmosphere moistened significantly but little rainfall occurred. The experiment-mean wind diurnal cycle was dominated by mainland Mexico and consisted of a near-surface westerly sea breeze along with two easterly return flows, one at 2–3 km and another at 5–6 km. Each of these altitudes experienced nighttime cloudiness. The corresponding modulation of the radiative cloud forcing diurnal cycle provided a slight positive feedback upon the sea surface temperature. Two findings were notable. One was an advective warming of over 1°C in the oceanic mixed layer temperature associated with the 13 July surge. The second was the high nighttime cloud cover fraction at 5–6 km, dissipating during the day. These clouds appeared to be thin, stratiform, slightly supercooled liquid-phase clouds. The preference for the liquid phase increases the likelihood that the clouds can be advected farther from their source and thereby contribute to a higher-altitude horizontal moisture flux into the United States.
Abstract
An algorithm to compute the magnitude of humidity gradient profiles from the measurements of the zeroth, first, and second moments of wind profiling radar (WPR) Doppler spectra was developed and tested. The algorithm extends the National Oceanic and Atmospheric Administration (NOAA)/Environmental Technology Laboratory (ETL) Advanced Signal Processing System (SPS), which provides quality control of radar data in the spectral domain for wind profile retrievals, to include the retrieval of humidity gradient profiles. The algorithm uses a recently developed approximate formula for correcting Doppler spectral widths for the spatial and temporal filtering effects. Data collected by a 3-beam 915-MHz WPR onboard the NOAA research vessel Ronald H. Brown (RHB) and a 5-beam 449-MHz WPR developed at the ETL were used in this study. The two datasets cover vastly different atmospheric conditions, with the 915-MHz shipborne system probing the tropical ocean atmosphere and the 449-MHz WPR probing continental winter upslope icing storm in the Colorado Front Range. Vaisala radiosonde measurements of humidity and temperature profiles on board the RHB and the standard National Weather Service (NWS) radiosonde measurements at Stapleton, Colorado, were used for comparisons. The cases chosen represent typical atmospheric conditions and not special atmospheric situations. Results show that using SPS-obtained measurements of the zeroth, first, and second spectral moments provide radar-obtained humidity gradient profiles up to 3 km AGL.
Abstract
An algorithm to compute the magnitude of humidity gradient profiles from the measurements of the zeroth, first, and second moments of wind profiling radar (WPR) Doppler spectra was developed and tested. The algorithm extends the National Oceanic and Atmospheric Administration (NOAA)/Environmental Technology Laboratory (ETL) Advanced Signal Processing System (SPS), which provides quality control of radar data in the spectral domain for wind profile retrievals, to include the retrieval of humidity gradient profiles. The algorithm uses a recently developed approximate formula for correcting Doppler spectral widths for the spatial and temporal filtering effects. Data collected by a 3-beam 915-MHz WPR onboard the NOAA research vessel Ronald H. Brown (RHB) and a 5-beam 449-MHz WPR developed at the ETL were used in this study. The two datasets cover vastly different atmospheric conditions, with the 915-MHz shipborne system probing the tropical ocean atmosphere and the 449-MHz WPR probing continental winter upslope icing storm in the Colorado Front Range. Vaisala radiosonde measurements of humidity and temperature profiles on board the RHB and the standard National Weather Service (NWS) radiosonde measurements at Stapleton, Colorado, were used for comparisons. The cases chosen represent typical atmospheric conditions and not special atmospheric situations. Results show that using SPS-obtained measurements of the zeroth, first, and second spectral moments provide radar-obtained humidity gradient profiles up to 3 km AGL.
The System Demonstration and Integration Division of the Environmental Technology Laboratory and the Battlefield Environment Directorate of the U.S. Army Research Laboratory have designed and built the Mobile Profiler System (MPS). The MPS is an integrated system of ground-based and satellite-borne remote sensors that measure nearly continuous wind and temperature profiles from the surface up through the troposphere. Ground-based sensors include a 924-MHz phased-array wind and temperature profiler, a four-channel microwave radiometer, a surface meteorological tower, and a balloon sounding system. Although MPS was initially developed for military applications, the nonmilitary environmental applications are numerous and significant.
This paper provides an overview of the instrumentation, software networking, data processing, data integration, and near real-time-data display capabilities currently incorporated into the MPS. Initial results from the first field tests (Los Angeles Free-Radical Study, 3–24 September 1993) demonstrate the ability of MPS to observe the complex meteorological structures associated with high-pollution events within the Los Angeles Basin.
The System Demonstration and Integration Division of the Environmental Technology Laboratory and the Battlefield Environment Directorate of the U.S. Army Research Laboratory have designed and built the Mobile Profiler System (MPS). The MPS is an integrated system of ground-based and satellite-borne remote sensors that measure nearly continuous wind and temperature profiles from the surface up through the troposphere. Ground-based sensors include a 924-MHz phased-array wind and temperature profiler, a four-channel microwave radiometer, a surface meteorological tower, and a balloon sounding system. Although MPS was initially developed for military applications, the nonmilitary environmental applications are numerous and significant.
This paper provides an overview of the instrumentation, software networking, data processing, data integration, and near real-time-data display capabilities currently incorporated into the MPS. Initial results from the first field tests (Los Angeles Free-Radical Study, 3–24 September 1993) demonstrate the ability of MPS to observe the complex meteorological structures associated with high-pollution events within the Los Angeles Basin.
Abstract
This paper examines the performance of satellite sounder atmospheric vertical moisture profiles under tropospheric conditions encompassing moisture contrasts driven by convection and advection transport mechanisms, specifically Atlantic Ocean Saharan air layers (SALs), tropical Hadley cells, and Pacific Ocean atmospheric rivers (ARs). Operational satellite sounder moisture profile retrievals from the Suomi National Polar-Orbiting Partnership (SNPP) NOAA Unique Combined Atmospheric Processing System (NUCAPS) are empirically assessed using collocated dedicated radiosonde observations (raobs) obtained from ocean-based intensive field campaigns. The raobs from these campaigns provide uniquely independent correlative truth data not assimilated into numerical weather prediction (NWP) models for satellite sounder validation over oceans. Although ocean cases are often considered “easy” by the satellite remote sensing community, these hydrometeorological phenomena present challenges to passive sounders, including vertical gradient discontinuities (e.g., strong inversions), as well as persistent uniform clouds, aerosols, and precipitation. It is found that the operational satellite sounder 100-layer moisture profile NUCAPS product performs close to global uncertainty requirements in the SAL/Hadley cell environment, with biases relative to raob within 10% up to 350 hPa. In the more difficult AR environment, bias relative to raob is found to be within 20% up to 400 hPa. In both environments, the sounder moisture retrievals are comparable to NWP model outputs, and cross-sectional analyses show the capability of the satellite sounder for detecting and resolving these tropospheric moisture features, thereby demonstrating a near-real-time forecast utility over these otherwise raob-sparse regions.
Abstract
This paper examines the performance of satellite sounder atmospheric vertical moisture profiles under tropospheric conditions encompassing moisture contrasts driven by convection and advection transport mechanisms, specifically Atlantic Ocean Saharan air layers (SALs), tropical Hadley cells, and Pacific Ocean atmospheric rivers (ARs). Operational satellite sounder moisture profile retrievals from the Suomi National Polar-Orbiting Partnership (SNPP) NOAA Unique Combined Atmospheric Processing System (NUCAPS) are empirically assessed using collocated dedicated radiosonde observations (raobs) obtained from ocean-based intensive field campaigns. The raobs from these campaigns provide uniquely independent correlative truth data not assimilated into numerical weather prediction (NWP) models for satellite sounder validation over oceans. Although ocean cases are often considered “easy” by the satellite remote sensing community, these hydrometeorological phenomena present challenges to passive sounders, including vertical gradient discontinuities (e.g., strong inversions), as well as persistent uniform clouds, aerosols, and precipitation. It is found that the operational satellite sounder 100-layer moisture profile NUCAPS product performs close to global uncertainty requirements in the SAL/Hadley cell environment, with biases relative to raob within 10% up to 350 hPa. In the more difficult AR environment, bias relative to raob is found to be within 20% up to 400 hPa. In both environments, the sounder moisture retrievals are comparable to NWP model outputs, and cross-sectional analyses show the capability of the satellite sounder for detecting and resolving these tropospheric moisture features, thereby demonstrating a near-real-time forecast utility over these otherwise raob-sparse regions.
